Operating channel/insufflation port assemblies are disclosed herein which facilitate the operation of percutaneous surgical procedures with remotely operable instrumentation. In one of the disclosed assemblies, an operating channel/insufflation port member defines an operating channel sized to receive remotely operable instrumentation, and an insufflation lumen. The port assembly is anchorable in place, extending percutaneously into the stomach with remotely operable instrumentation being advanceable through the operating channel and into the stomach, and with CO.sub.2 being passable into the stomach through the insufflation lumen. An insufflation valve member, connectable to said insufflation port, provides means for variably controlling the supply of CO.sub.2 into the stomach while a sealing member prevents gas leakage through the operating channel during operation/insufflation by providing a seal between the port member and the remotely operable instrumentation received therethrough.In a second disclosed assembly, the operating channel/insufflation port member defines an operating channel sized to receive remotely operable instrumentation, and a dual purpose inflation/insufflation lumen. The port assembly is anchorable in place by a balloon which is inflatable through the inflation/insufflation lumen. After the balloon has been inflated, an inflation/insufflation tube within the inflation/insufflation lumen is advanced to seal the inflated balloon and open an insufflation port, through which a positive pressure may be maintain within the stomach during a subsequent surgical procedure performed through the operating channel. Also provided are a set of seals which prevent gas leakage both during and after operation/insufflation.